Safety suture cutting device and related methods

ABSTRACT

A sheath for use with a scalpel cutting device including a sheath body configured to cover a scalpel blade at a distal end of a scalpel cutting device. The sheath advantageously may include a plurality of slots formed therein. Providing two or more slots provides additional functionality and/or ease of manufacturing. A single sheath configuration including a plurality of slots (e.g., two) may be manufactured so as to be used with scalpels including somewhat different blade configurations (e.g., which may require a slightly different slot location). Such a universal sheath allows a single sheath design to be used with multiple scalpels, easing manufacture and reducing costs. In addition, depending on the particular location of the slots and the configuration of the scalpel blade, the different slots may each intersect the scalpel blade and provide different characteristics for cutting a suture.

BACKGROUND OF THE INVENTION

1. The Field of the Invention

The present invention is in the field of medical devices, for examplescalpels and other surgical cutting devices.

2. The Relevant Technology

Medical practitioners often close a wound or opening within a patient(e.g., during surgery) with sutures. Scalpels are often used as neededin performing the surgery, and then are often used for cutting the endsof sutures employed to close up the wound or opening within thepatient's tissue. Depending on the nature of the procedure, sutures canbe placed adjacent to a main artery or vein, and as such, anymisplacement of the scalpel when cutting the suture (e.g., caused by anaccidental sneeze, cough, or otherwise) could potentially be disastrous.As an alternative, it is possible to cut the sutures with scissors, butthis requires an additional step and can be something of a nuisance tothe practitioner, as the practitioner already has a scalpel handy.

Many scalpels include a safety sheath that covers the blade end of thescalpel. In order to use the blade (e.g., for cutting tissue or asuture) the sheath must be retracted or removed, or a retractable blademust be extended beyond the sheath, so as to expose the blade for use.

Some efforts have been made to provide an ability to access the scalpelblade for cutting a suture while the blade is safely sheathed so as toprevent accidental cuts to the patient and/or practitoner. One suchconfiguration is shown in U.S. Patent Application 2009/0157110, whichincludes a notch opening 17 in the side of the sheath 18 to allow asuture to be cut without exposing blade 20. As the suture is insertedinto notch opening 17, tension between the suture and the blade 20 isused to cut the suture.

Another configuration is shown in FIG. 1B, which is taken from U.S.Patent Application 2005/0234481, and which discloses a dedicated suturecutting device in which the blade 115 is somewhat protected within analcove at the distal end of the device. Similar to the device shown inFIG. 1A, the suture is pulled tight against the blade and tensionbetween the blade and suture cuts the suture. Such a device is notcapable of performing the traditional functions of a scalpel.

Although suture-cutting devices have been proposed, there still exists aneed for improved configurations that effectively sheath the blade fromaccidental exposure, while providing easy, fast, and efficient cuttingof a suture.

SUMMARY OF THE INVENTION

The present invention is directed to a sheath for use with a scalpelcutting tool, as well as scalpel cutting tools including such sheaths.In one embodiment, the device includes a sheath body configured to covera scalpel blade at a distal end of a scalpel cutting device. The sheathbody includes a suture guide slot formed into a surface of the body, andthe slot extends from a first end at the edge of the sheath body to asecond end adjacent the scalpel blade so that the slot intersects theblade, and the blade is exposed within the slot (i.e., at the second endor “bottom” of the slot), but is otherwise protected by the sheath. Theslot includes a width defined by first and second opposed guiding sidewalls, and the blade is non-perpendicular relative to the slot. Theangle between the first side wall of the slot and the scalpel blade attheir point of intersection is advantageously greater than 105° and lessthan 180°.

In the case where the first and second side walls of the suture guideslot are parallel and the blade is straight, the angle between thesecond side wall and the blade at their point of intersection will beequal or approximately equal to 180° minus the angle between the firstside wall and the blade at their point of intersection (i.e., the twoangles can sum to 180°). Generally speaking, the side wall with thelargest angle relative to the blade will have the shortest length, andvice-versa. In the case where the side walls are not parallel (e.g.,they converge toward the blade) and/or the blade is not straight butcurved, the sum of the two angles may not be 180°. Nevertheless, ingeneral, when the first angle is obtuse (i.e., greater than)90° thesecond angle will typically be acute (i.e., less than 90°).

In this embodiment, the slot walls and blade do not intersect oneanother in a substantially perpendicular configuration, but a moregradual angle of intersection is provided. This is advantageous as thecutting of the suture thus does not rely only on the tension between asuture that is perpendicular to the blade, and which is then pulledthrough the blade. Rather, the angle is significantly greater than 90°and the suture is pulled in a direction having a major component ofmotion that is parallel to the blade, while under slight tension, andwith a minor component of motion that is perpendicular to the blade.This introduces a slicing action and allows the suture to be cut withconsiderably less force than is required when attempting to simply pullthe suture through the blade where the orientation of the suture andblade are perpendicular relative to one another, and in which theapplied force is largely perpendicular to the blade.

Such slicing or shearing action requires significantly less force to cutthe suture because the component of motion or force that isperpendicular to the blade is reduced compared to when the angle is 90°.In other words, the suture motion has a significant component of motionthat is parallel to the blade as the suture is pulled along the lengthof the blade within the slot. The interaction of the slot and suturecauses the blade to progressively slice through the suture from theside, rather than there being no substantial movement of the suturealong the blade length as is the case when the pulling or cutting forceis perpendicular to the blade surface.

According to another embodiment, the device comprises a sheath body anda slot formed in the sheath body that intersects the scalpel blade sothat the scalpel blade is exposed only within the slot, and in which theratio of the length of the shortest slot side wall to the slot width isat least 2, more preferably at least about 3, and most preferably atleast about 4. Such a ratio of slot depth to width is advantageous as itprovides a greater safety factor to a user so as to keep the sharp bladewell recessed and protected within the sheath compared to shallower aslot, and minimizes the tendency of the suture to be accidentallywithdrawn from the slot as a result of inadvertently jerking orside-to-side movement of the suture. Such a ratio is independent of thesuture diameter. For example, a larger diameter suture may benefit froma greater slot depth, as well as a greater slot width. When employedwith a suture of typical diameter (e.g., about 0.1 to about 0.25 mm),the length of the shortest slot side wall may be at least 3 mm, morepreferably at least about 4 mm, and more preferably at least about 5 mmfrom the first slot end at the edge of the sheath to where the slotintersects with the blade. In addition to better retaining the suturewithin the slot, such ratios and slot depths are particularly beneficialin keeping the sharp blade well away from the exterior end or side ofthe sheath so as to prevent accidental cuts.

The sheath may be separate and removable from the scalpel cutting tool,in which case the sheath is configured to be positioned over the distalblade end of the scalpel. In other embodiments, the sheath may beattached to the scalpel cutting tool so as to not be removabletherefrom, but in which either the blade or sheath may be retracted,selectively exposing the blade.

An advantage of embodiments that include a suture guide slot at theforward end of a relatively narrow sheath is that the device can bemaneuvered longitudinally to cut sutures in restricted spaces. The spacein which such devices can cut may be limited only by the width of thesheath. This is in contrast to suture scissors, which often require muchgreater space to operate properly, or a suture cutting blade with thesuture guide slot positioned on the side and that must be movedlaterally (e.g., perpendicular to the longitudinal axis of the device)rather than longitudinally when cutting.

In some embodiments, the sheath may include spacing means for providinga desired blade height or distance from the skin or tissue surface. Thiscan provide several desired functions, including leaving a suture endwith a desired length and/or preventing inadvertent cutting of thesuture knot, which should be positioned between the blade and thepatient's tissue surface. An example of spacing means includes one ormore rails or protrusions on a side of the sheath. The sheath canoptionally include differently sized rails or protrusions on oppositesides of the sheath that maintain the cutting blade at differentdistances from the tissue surface to provide a practitioner with theability to cut at different heights or distances from the skin dependingon which side of the sheath is positioned next to the tissue surface.

In one embodiment the sheath includes a plurality of slots formed in thesheath. Such a configuration provides additional functionality and/orease of manufacturing. For example, a single sheath configurationincluding a plurality of slots (e.g., two) may be manufactured so as tobe used with scalpels including somewhat different blade configurations(e.g., which may require a slightly different slot location). Such auniversal sheath allows a single sheath design to be used with multiplescalpels, easing manufacture and reducing costs. In addition, dependingon the particular location of the slots and the configuration of thescalpel blade, the different slots may each intersect the scalpel bladeand provide different characteristics for cutting a suture. For example,one slot may intersect the blade at a relatively shallow angle,providing the shearing benefits described herein, while another slot mayintersect the blade at a less shallow angle nearer 90°, which may stillbe suitable for cutting relatively thin, low strength sutures.

These and other benefits, advantages and features of the presentinvention will become more fully apparent from the following descriptionand appended claims, or may be learned by the practice of the inventionas set forth hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the manner in which the above recited and other benefits,advantages and features of the invention are obtained, a more particulardescription of the invention briefly described above will be rendered byreference to specific embodiments thereof which are illustrated in theappended drawings. The drawings depict only typical embodiments of theinvention and are not therefore to be considered limiting of its scope.

FIG. 1A is cross-sectional view through a prior art scalpel including anotch for cutting a suture;

FIG. 1B is a perspective view of a prior art dedicated suture cuttingdevice;

FIG. 2A is a front side view of an exemplary scalpel including aprotective sheath having a slot formed in a distal end surface thereofaccording to the present invention;

FIG. 2AA is a close up view of the slot and sheath of FIG. 2A;

FIG. 2B is a front side view of an alternative scalpel including aprotective sheath having a slot formed in a distal end surface thereofaccording to the present invention;

FIG. 2BB is a close up view of the slot and sheath of FIG. 2B;

FIG. 3A is a front side view of another scalpel including a protectivesheath having a slot formed in a distal end surface thereof according tothe present invention;

FIG. 3AA is a close up view of the slot and sheath of FIG. 3A;

FIG. 3B is a front side view of another scalpel including a protectivesheath having a slot formed in a distal end surface thereof according tothe present invention;

FIG. 3BB is a close up view of the slot and sheath of FIG. 3B;

FIG. 4 is a front side view of the distal end of another scalpelincluding a protective sheath having a slot formed in a side surfacethereof according to another embodiment of the present invention;

FIG. 5A is a partial cross-sectional view showing the distal end of ascalpel blade and sheath slot similar to that of FIG. 2BB in which asuture to be cut is positioned at the intersection of the slot andblade;

FIG. 5B is a partial cross-sectional view similar to that shown in FIG.5A in which the suture has advanced along the exposed blade surface,slicing into the suture;

FIG. 6 illustrates how an exemplary safety suture cutting device is ableto cut a suture in a restricted space;

FIGS. 7A and 7B are distal end views of a sheath having rails thatprovide a predetermined height or distance between the suture cuttingblade and the skin surface;

FIGS. 8A and 8B are front side views of an exemplary sheath including aplurality of slots for use with different types of scalpel blades; and

FIG. 8C is a distal end view of a sheath similar to that of FIG. 8Aincluding rails providing a predetermined height or distance between theblade and a skin surface.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

I. Introduction

In one embodiment, the present invention is directed to a sheath for usewith a scalpel cutting device including a sheath body configured tocover a scalpel blade at a distal end of a scalpel cutting device. Thesheath advantageously includes a slot formed therein that extends from afirst end at an edge of the sheath body to a second end adjacent thescalpel blade so that the slot intersects the blade and the blade isexposed only within the second end of the slot. The blade surface isnon-perpendicular relative to the slot side walls, such that generallyone side wall will be shorter than the other. The slot is furtheradvantageously configured such that an angle between the first guidingside wall (e.g., the shorter side wall) of the slot and the scalpelblade at the point of intersection is greater than 105° and less than180°. Where the slot side walls are parallel and the blade is straight,the angle between the second side wall and the blade at intersectionwill be supplementary to the first angle. Although the angles may notsum to 180° in embodiments including non-parallel slot side walls and/orcurved blades, in general when the first angle is obtuse, the secondangle will be acute.

In any case, the configuration advantageously allows a suture insertedwithin the slot to be sheared or sliced as the suture is pulled alongthe blade edge rather than simply pulled perpendicularly through theblade. Slicing the suture in this manner greatly decreases overallapplied force, and particularly the component of the force applied in adirection perpendicular to the blade, which eases cutting of the suture,while also minimizing or preventing any tendency of the suture to tearthrough the patient's tissue as a result of the applied forces.

In another embodiment, the slot of the sheath is specifically configuredto include a ratio of the length of the shortest slot side wall to theslot width that is at least 2. Such a ratio minimizes or prevents thetendency of the suture to accidentally become dislodged from the slot asa result of inadvertent movement. Such a ratio also provides sufficientslot depth to prevent accidental cuts caused by a blade which isdisposed closer to the edge of the protective sheath. Even greaterratios of slot side wall length to slot width (e.g., at least about 3 orat least about 4) are even more effective at retaining the suture withinthe slot and preventing accidental cuts.

II. Exemplary Safety Suture Cutting Devices

FIG. 2A shows an exemplary scalpel 100 including a proximal gripping end102 and a distal end 104 to which is attached a blade 106. A retractablesheath 108 is coupled over the distal end 104 so as to selectively coverand uncover blade 106. In the illustrated configuration, sheath 108 isfully extended, so as to fully cover blade 106. Retractable sheath 108includes a tab 110 that rides within a guide slot 112 that allows thesheath to be selectively slid from the sheathed configuration shown to aconfiguration (not shown) in which blade 106 is exposed, extendingthrough the distal end of sheath 108. Although one configuration of theretraction mechanism is shown, it will be understood that otherretraction mechanisms may be employed. For example, in an alternativeembodiment, it may be the blade that is retractable within a protectivesheath (see FIGS. 3A-3B). In another embodiment, neither the sheath northe blade may be retractable, but the sheath may be separate andremovable from the scalpel. Such a removable sheath may simply becoupled or otherwise disposed over the blade so as to cover and protectthe blade from accidental contact with another surface.

Sheath 108 includes a slot 114 formed therein. In the illustratedexample, slot 114 extends from the distal end surface 116 of sheath 108towards the sharp cutting surface of blade 106. Slot 114 intersectsblade 106, as shown perhaps most clearly in FIG. 2AA. Slot 114 is shownin FIGS. 2A-2AA as being curved, while a straight slot is shown in FIGS.2B-2BB. Slot 114 includes a first side wall 118 that acts as a guidesurface on one side of slot 114 and a second side wall 120 that acts asanother guide surface on the other side of slot 114. The width of theslot 114 is defined between side walls 118 and 120.

As seen in FIG. 2AA, a suture 122 can be introduced into slot 114 inpreparation for easily and efficiently cutting the suture. For example,suture 122 may be guided downward along side wall 118 until it reachesthe intersection of side wall 118 with blade 106. Because blade 106advantageously forms an angle relative to side wall 118 that is greaterthan 90° and the slot 114 is sufficiently wide relative to the suturediameter, the suture 122 may be pulled across blade 106 towards oppositeside wall 120, slicing through suture 122 with relatively littledownward force applied. In other words, only a minor component of theapplied force is directed perpendicular to the blade 106, while themajor component or vector of the applied force is directed parallel tothe blade 106. As a result of such a slicing action and configuration,the forces transmitted upwards through the suture to the patient'stissue are minimized. By comparison, when applying a force that isentirely (or nearly so) perpendicular to the blade without anysubstantial translation of the suture along the blade surface, not onlyis the magnitude of the component of the applied force that isperpendicular to the blade significantly greater, but the overallmagnitude of the applied force must also be greater than that applied inthe inventive embodiments. Such higher forces increase the tendency totear the suture through the patient's flesh.

For example, before cutting, the opposite end of the suture may bestitched into the patient's tissue. As a result, it is desirable tominimize pulling forces on the suture that might otherwise pull thesuture, cutting through the patient's tissue (e.g., similar to a cheesewire). The described configurations provide slot to blade angles andslot widths that are configured so as to minimize such tissue cuttingforces. Preferably, the angle between the side wall 118 of the slot andthe blade 106 is between about 130° and about 170°, more preferablybetween about 150° and about 170°. For example, the configuration shownin FIG. 2AA includes an angle of about 160° between side wall 118 andblade 106.

It will be appreciated that the angle formed between second side wall120 of the slot and the blade will be supplementary to the abovedescribed angles where the side walls 118 and 120 are parallel and theblade is substantially straight within the slot 114. Although inembodiments including non-parallel side walls and/or blades exhibitingsubstantial curvature within the exposed portion of the slot the twoangles may not sum to 180°, in general the angle associated with theshorter side wall will be obtuse, while the angle associated with thelonger side wall will be acute.

The described configuration that introduces a slicing action whencutting the suture is particularly beneficial for use with strong,difficult to cut sutures. For example, some polymeric sutures are sostrong that they are difficult if not impossible as a practical matterto cut by simply pulling the suture perpendicularly through a bladewithout tearing the just completed stitched portion of the suturethrough the patient's flesh. The particular slot to blade angleprovided, as well as the blade length exposed within the slot selectedmay depend on the strength of sutures to be cut with the device. Forexample, stronger sutures may require a shallower angle (i.e., closerto180°) and/or a greater ratio of exposed blade length to suturediameter. Relatively weaker sutures may be sliced without anycheese-wire effect of tearing through the patient's flesh with a sharperangle (i.e., closer to 105°) and/or a lower ratio of exposed bladelength to suture diameter.

It is also noted that the width of slot 114 is significantly greaterthan the diameter or thickness of the suture 122 to be cut. The term“diameter” will be used hereinafter, although it will be understood thatthe suture may have a cross-section that is other than round, in whichthe diameter referred to is the suture thickness. This width of the slot114 provides sufficient space for the suture to be pulled along theblade 106 while a small downward force component is applied so that theblade slices into the suture as it is pulled along blade 106. FIGS.5A-5B, described in further detail below, show such a progressiveslicing action. For example, the width of slot 114 may be such so as toprovide a length of exposed blade 106 within slot 114 that is at leastabout 1.5 times the diameter of the suture 122 to be cut. In oneembodiment, the exposed blade length within slot 114 may be at leastabout 2 times the suture diameter; in another embodiment the exposedblade length may be between about 4 times and about 12 times the suturediameter. For example, the arc length of blade 106 illustrated in FIG.2AA is about 6 times the diameter of suture 122. The width of slot 114should not be so great as to allow inadvertent cutting of apractitioner's finger or other appendage.

FIGS. 2B-2BB illustrate another embodiment of a scalpel 100′ that issimilar to that shown in FIGS. 2A-2AA, but in which the slot 114′ issubstantially straight rather than curved. In addition, scalpel 100′further includes a guide member 124 disposed adjacent slot 114′ thatextends beyond the distal mouth of slot 114′, adjacent sidewall 120 soas to aid in guiding suture 122 into slot 114′. Such a guide member isbeneficial in helping to introduce the suture into slot 114′ (e.g., byplacing suture 122 in contact with guide 124 and then pulling suture 122downward, where it is guided into slot 114′). Guide member 124 mayalternatively be positioned adjacent guiding side wall 118. Such a guidemember may be provided with any of the embodiments described herein.

In addition, the mouth of slot 114′ is shown as being flared inembodiment 100′, while that of FIGS. 2A-2AA is not flared. Although bothslots 114 and 114′ are shown as having a substantially constant widthover substantially the entire depth of the slot, it will be understoodthat alternative embodiments may include non-parallel side walls so thatthe width varies. For example, one embodiment may include side wallsthat converge towards the blade, which facilitates easier introductionof the suture into the slot. In another example, an embodiment mayinclude a mouth of a given width, which widens as the slot approachesthe blade 106. Such a configuration may be beneficial in helping toprevent accidental release of the suture 122 after entrance into theslot, while also providing the desired ratio of exposed blade length tosuture diameter where the slicing occurs (i.e., at the blade edge).Where the width of the slot varies, the sidewalls may be smooth or mayinclude an abrupt transition, as desired.

FIGS. 3A-3AA illustrate another embodiment of a scalpel 200 including aproximal gripping end 202 and a distal end 204 within which is disposeda blade 206. In this embodiment, it is the blade 206 that is extendablebeyond and retractable within the distal end 204 of the scalpel 200.Distal end 204 includes a sheath 208 within which blade 206 may beselectively retracted and protected. Retractable blade 206 may beattached to a slidable member 210 that rides within a guiding slot 212that allows the blade 206 to be selectively slid from the sheathedconfiguration (shown) to a configuration in which blade 206 extendsbeyond distal end 216 of sheath 208. It will be understood that otherretraction mechanisms may be employed, or that the sheath may beseparate and removable from the scalpel cutting tool.

Similar to the above described embodiments, sheath 208 includes a slot214 formed therein. In the illustrated example, slot 214 extends fromthe distal end surface 216 of sheath 208 towards blade 206. Slot 214intersects blade 206, as shown perhaps most clearly in FIG. 3AA. Slot214 is shown in FIGS. 3A-3AA as being substantially straight andvertical (i.e., parallel to a longitudinal axis of the scalpel 200),rather than curved as shown in FIGS. 2A-2AA. Slot 214 includes a firstside wall 218 that acts as a guide surface on one side of slot 214 and aparallel second side wall 220 that acts as another guide surface on theopposite side of slot 214. The width of the slot 214 is defined betweenside walls 218 and 220. Another difference of scalpel 200 is that blade206 is shown as having a substantially straight cutting edge, ratherthan the curved cutting edge shown in FIGS. 2A-2BB. In addition, thedistal end 216 of sheath 208 is illustrated as flat (i.e., perpendicularto a longitudinal axis of the scalpel), rather than including a curveddistal end surface as the embodiments of FIGS. 2A-2BB. It will beunderstood that various sheath and blade configurations may be usedwithin any given embodiment. For example, one embodiment (not shown) mayinclude a straight edged blade as in FIG. 3A-3BB with a curved endsheath as in FIG. 2A-2BB.

FIGS. 3B-3BB illustrate another embodiment of a scalpel 200′ similar tothat of FIG. 3A-3AA, but in which the mouth of slot 214′ is flaredrather than square, as is the mouth of slot 214. Flaring may aid a userin introducing the suture 122 into the slot.

Table I below shows shorter side wall to blade edge angle information(Angle), exposed blade length to suture diameter ratios (Ratio 1), andshorter side wall length to slot width ratios (Ratio 2) for theembodiments shown in FIGS. 2AA, 2BB, 3AA, 3BB, and FIG. 4.

TABLE I Example Angle Ratio 1 Ratio 2 FIG. 2AA 158° 6.1 3.8 FIG. 2BB149° 4.8 2.9 FIG. 3AA 169° 10.9 2.4 FIG. 3BB 169° 10.9 2.4 FIG. 4  90°2.0 6.5

FIG. 4 illustrates another alternative embodiment. As will be readilyappreciated, in this embodiment, both the side walls of slot 314 form anangle relative to the blade 306 that is less than 105° (e.g., about 90°for each), and the slot 314 is formed into a lateral side 316 a, ratherthan the distal end 316 of sheath 308. As such, this embodiment may beless preferred for reasons described above relative to the preferredangles that are greater than 90° and the associated slicing actionachieved, but this embodiment illustrates other desirable features thatmay be incorporated into the inventive devices.

For example, scalpel 300 includes a slot 314 having a ratio of thelength of the shortest side wall of slot 314 to slot width that is atleast 2, more preferably at least about 3. In some embodiments, theratio may be even greater (e.g., at least about 4). Such a ratio isindependent of the suture diameter to be cut. Such a configurationprovides an additional degree of safety over the prior art embodimentshown in FIG. 1A, in which the slot appears wide and short rather thanexhibiting the greater ratios herein described. In such embodiments, thehigher ratio of side wall length to slot width aids in retaining thesuture within the slot 314 once introduced. With a shallower slot, thesuture may easily become dislodged from the slot, leading to frustrationand wasting the time of the practitioner. In addition, shallow and wideslots may position the blade dangerously close to the notch formed inthe side of the sheath.

When used with typically sized sutures (e.g., about 0.1 mm to about 0.25mm in diameter), the length of the shortest side wall may be at least 3mm, more preferably at least about 4 mm, and even more preferably atleast about 5 mm. Even greater lengths are possible (e.g., 8 mm or 10mm). Of course, ratios of shortest side wall to slot width of at least2, at least 3, at least 4 and slot depths of at least 3 mm, 4 mm, 5 mmor more as described above may be included within the embodimentsillustrated and described above in conjunction with FIGS. 2A-3BB, whichconfigurations may be particularly preferred as providing collectivelythe most benefits. In addition, the slots of any of the embodimentsshown in FIGS. 2A-3BB may be formed into a lateral side, rather than thedistal end of the sheath.

FIG. 5A illustrates a further close up view similar to the scalpelembodiment shown in FIG. 2BB, in which the suture 122 is positioned atthe intersection of guiding side wall 118 and blade 106. As shown inFIG. 5B, as the suture is pulled along the edge of blade 106, blade 106slices into the side of suture 122. The applied force includes a minorcomponent that is in a direction perpendicular to the blade surface anda major component that is in a direction parallel to the blade surface.For example, as seen in FIG. 5B the suture 122 has advanced about halfway along the length of the exposed blade edge, slicing nearlycompletely through suture 122. Suture 122 will be completely severedprior to reaching opposite guiding side wall 120. Of course, the devicemay be used by initially positioning the suture 122 at the intersectionof side wall 120 and blade 106 and advancing along blade 106 in theopposite direction, although it may be preferred to progress “down” theblade 106, rather than “up” the blade 106.

Each of the described embodiments advantageously provides the ability tosafely and efficiently cut a suture without having to extend the scalpelblade to an unprotected position in order to perform the cutting.

As illustrated in FIG. 6, an advantage of embodiments that include asuture guide slot 614 at the forward end 616 of a relatively narrowsheath 608 is that the device 600 can be maneuvered longitudinally(i.e., in a direction that is generally parallel to the longitudinalaxis A of the device) to cut sutures 622 in a restricted space definedby obstructions 604 on one or both sides of the suture knot 606. Thespace in which such devices can cut may be limited only by the width Wof the sheath 608. This is in contrast to suture scissors, which oftenrequire much greater space to operate properly, or a suture cuttingblade with the suture guide slot positioned on the side and that must bemoved laterally (e.g., perpendicular to the longitudinal axis A of thedevice) rather than longitudinally when cutting. The width W can beconfigured to be about 1 inch (about 25 mm) or less, for example, notmore than about 0.5 inch so as to allow the device to slide easilybetween closely spaced obstacles, cutting a suture disposedtherebetween. For example, with scissors, if the practitioner wererequired to open the scissor blades to more than width W, then theconvenience and/or effectiveness of the cutting is negatively affected.With a device including a suture guide slot positioned on the side, thepractitioner may be required to orient the device and blade so as toface the patient's tissue, which can result inadvertent cuts to thepatient.

As illustrated in FIGS. 7A and 7B, the sheath 700 may include one ormore spacing rails or protrusions 702 a, 702 b on one or both surfacesfor providing a desired height or distance 704 a of the cutting blade706 from the skin or tissue surface 708. This can provide severaldesired functions, including leaving a suture end 710 with a desiredlength 704 a and/or preventing inadvertent cutting of the suture knot714, which should be positioned between the blade 706 and the patient'stissue surface 708. As shown in FIG. 7A, first spacing rails orprotrusions 702 a on a first side of the sheath 700 provide a firstheight or distance 704 a of the blade 706 from the skin or tissuesurface 708. As shown in FIG. 7B, second spacing rails or protrusions702 b on a second side of the sheath 700 provide a second larger heightor distance 704 b of the blade 706 from the skin or tissue surface 708.Thus, the distance 704 a, 704 b that the cutting blade 706 is maintainedfrom the tissue surface 708 can be changed by orienting either the firstside or second side of the sheath 700 adjacent to the tissue surface708. The spacing rails or protrusions 702 a, 702 b comprise examples ofspacing means within the scope of the invention, although otherstructures known in the art or described herein can provide spacingmeans (e.g., guide member 124 described above may protrude from the sideof the sheath so as to provide spacing means).

The spacing means can advantageously be used to cut a pair of sutureends the same length to provide a cleaner, more professional look ascompared to random lengths that often occur when cutting sutures usingscissors or an unguided scalpel blade. In addition, the spacing meanscan ensure that the suture end has a desired length to preventinadvertent slipping and untying of a suture knot, as can occur when thesuture end is excessively short (e.g., less than 1 mm), particularlywhen using smooth polymeric sutures that have less friction and may bemore prone to slippage. Even worse, without such spacing means, thepractitioner may accidentally cut into the suture knot, requiringrestitching of the suture. The ability to cut the suture at apredetermined distance from the tissue surface greatly facilitates thesuture cutting process and eliminates guesswork and error inherent insuch procedures.

For example, if the minimum suture end length required by the procedureis 3 mm but the cutting tolerance to account for surgeon error and/orlimits in visibility is 3 mm, the surgeon might have to try to leave asuture end length of 6 mm to ensure that at least 3 mm of the sutureremains. This can leave messy looking and/or uncomfortable suture ends.Providing a device that ensures a predetermined suture end length of 3mm can simultaneously maximize safety, aesthetics and patient comfortwith little or no effort on the part of the surgeon.

According to one embodiment, the sheath and/or spacing means can beconfigured to provide a desired height or distance of the blade from thetissue surface that is one or more (e.g., two) of 1 mm, 1.5 mm, 2 mm,2.5 mm, 3 mm, 3.5 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 10 mm, or decimalincrements above, below or between these exemplary distances). By way ofexample, the blade height or distance from the tissue surface may be 3mm when a first side of the sheath is oriented toward the tissue surfaceand 5 mm when a second side of the sheath is oriented toward the tissuesurface. The device also may include means for raising or lowering theheight of the rails, protrusions or other spacing means in order toprovide greater adjustability of the blade height or distance from thetissue surface (e.g., a ratching mechanism).

Sheath 108 includes a slot 114 formed therein. In the illustratedexample, slot 114 extends from the distal end surface 116 of sheath 108towards the sharp cutting surface of blade 106. Slot 114 intersectsblade 106, as shown perhaps most clearly in FIG. 2AA. Slot 114 is shownin FIGS. 2A-2AA as being curved, while a straight slot is shown in FIGS.2B-2BB. Slot 114 includes a first side wall 118 that acts as a guidesurface on one side of slot 114 and a second side wall 120 that acts asanother guide surface on the other side of slot 114. The width of theslot 114 is defined between side walls 118 and 120.

FIGS. 8A and 8B illustrate an embodiment of a safety sheath 808including a plurality (e.g., at least two) of slots 814 a and 814 b.Each slot extends from distal end surface 816 of sheath 808 towards thesharp cutting surface of blade 806 or 806′. FIG. 8A shows the sheath 808in conjunction with a curved blade 806 similar to that shown in FIGS.2A-2AA, while FIG. 8B shows the sheath 808 in conjunction with astraight blade 806′ similar to that shown in FIGS. 3A-3AA.

Providing a sheath 808 with two or more slots provides ease ofmanufacturing benefits (i.e., the same sheath may be employed withdifferent scalpel configurations) so that a single sheath can bemanufactured and usable for use with multiple blade configurationsand/or sizes. In addition or alternatively, a sheath with multiple slotscan provide additional functionality as compared to a sheath includingonly a single slot. Of course, any of the other sheath configurationsdescribed herein may be modified by the addition of one or moreadditional slots.

Providing a sheath 808 with a plurality of slots may allow the sheath808 to be used with different scalpel configurations in which the exactlocation of the cutting edge of the blade may be in a somewhat differentlocation depending on the particular scalpel configuration. Providingsuch a universal sheath including a plurality of slots provides amanufacturing advantage, as the same sheath configuration may be usedwith different scalpel blade configurations (e.g., as shown in FIGS. 8Aand 8B) or sizes. For example, one of slots 814 a, 814 b may be locatedso as to provide a desired intersection with one type of scalpel blade(e.g., a curved blade such as that shown in FIG. 8A), while the otherslot may be located so as to provide a desired intersection with anothertype of scalpel blade (e.g., a straight blade such as that shown in FIG.8B) so as to provide the desired shearing action and/or shallowintersection between the blade and slot.

With regard to added functionality, when using a sheath 808 inconjunction with a straight blade 806′ such as that shown in FIG. 8B, apractitioner may typically use first slot 814 a as it may provide adesired shallow angle (e.g., greater than about 105° and less than 180°)and full extension across the slot no matter the exact retractionposition of blade 806′. In other words, one of the slots may provide oneangle between the side wall of the slot and the scalpel blade at anintersection of the two that is different from the angle providedbetween the side wall and the scalpel blade at an intersection of thetwo in the other slot.

When using the sheath 808 in conjunction with a curved blade 806 asshown in FIG. 8A, a practitioner may typically wish to use second slot814 b, which would provide a shallow shearing angle and a relativelylong distance along which the suture may be pulled so as to cut throughthe suture. Of course, should a practitioner desire, the suture may beintroduced into first slot 814 a of the embodiment shown in FIG. 8A,particularly where the suture may be relatively easy to cut through,e.g., where the length for a shearing action and/or a more shallowintersection angle is not necessary.

Similarly, where the second slot 814 b of the embodiment of FIG. 8B wereto intersect blade 806′, a suture may be introduced into this secondslot for cutting, where desired. In some combinations of the sheath withthe scalpel blade, the second slot may not provide an intersection witha particular scalpel blade, although intersection between the slot andblade is provided within at least one of the slots (e.g., typically atleast first slot 814 a will provide access to the scalpel blade).

According to one embodiment and as shown in FIG. 8C, where two slots areprovided, the portion of the sheath 826 may be reinforced and thickenedas compared to other portions adjacent slots 814 a and 814 b, as thisrelatively narrow middle pillar portion 826 may otherwise be prone tobreakage. In one embodiment, the thickening of middle pillar portion 826may be by forming a transversely thickened rail(s) or protrusion(s) 826a, 826 b at middle pillar portion 826 that extends from the top and/orbottom surface of sheath 808 so as to acts as an additional fixed lengthcutting rail guide in conjunction with other rails 802 a and 802 b(e.g., similar to rails 702 a and 702 b of FIGS. 7A-7B).

It will also be appreciated that the present claimed invention may beembodied in other specific forms without departing from its spirit oressential characteristics. The described embodiments are to beconsidered in all respects only as illustrative, not restrictive. Thescope of the invention is, therefore, indicated by the appended claimsrather than by the foregoing description. All changes that come withinthe meaning and range of equivalency of the claims are to be embracedwithin their scope. Additionally, as used in this specification and theappended claims, the singular forms “a,” “an” and “the” include pluralreferents unless the context clearly dictates otherwise.

What is claimed is:
 1. A scalpel cutting device comprising: a scalpelblade positioned at a distal end of an elongate portion of the scalpelcutting device, the scalpel blade having a straight cutting edge; asheath body configured to cover the scalpel blade in a covered position,the sheath and the blade movable between the covered position and anuncovered position in which the blade is exposed for cutting tissuethrough an opening in a distal end of the sheath; and a first slotformed in the sheath body, the first slot extending between first andsecond surfaces of the sheath body and extending inward from an edge ofthe distal end of the sheath body toward the blade, wherein: with thescalpel blade in the covered position, the first slot has a sidewallthat intersects the straight cutting edge at an angle between 105° and180° such that the first slot causes shearing of a suture sliding inwardtherethrough.
 2. The scalpel cutting device as recited in claim 1,wherein the sheath comprises a second slot formed in the sheath body,the second slot having a sidewall that intersects the straight cuttingedge at an angle between 105° and 180°.
 3. The scalpel cutting device asrecited in claim 2, wherein the side wall of the first slot intersectsthe scalpel blade at a different angle than the sidewall of the secondslot.
 4. The scalpel cutting device as recited in claim 1, wherein thefirst slot ends where the first slot intersects the straight cuttingedge.
 5. The scalpel cutting device as recited in claim 1, wherein thesheath further comprises spacing means for providing a desired height ordistance of the scalpel blade from a skin or tissue surface.
 6. Thescalpel cutting device as in claim 1, wherein the sheath furthercomprises one or more rails or protrusions extending from a surface ofthe sheath for providing a desired height or distance of the scalpelblade from a skin or tissue surface.
 7. The scalpel cutting device asrecited in claim 1, wherein the first side wall intersects the straightcutting edge at an angle between 130° and 170°.
 8. The scalpel cuttingdevice as recited in claim 1, wherein the first side wall intersects thestraight cutting edge at an angle between 150° and 170°.
 9. The scalpelcutting device as in claim 1, wherein the blade height above a tissuesurface in contact with the sheath is at least 1 mm.
 10. The scalpelcutting device as in claim 1, wherein the blade height above a tissuesurface in contact with the sheath is at least 3 mm.
 11. The scalpelcutting device as in claim 1, wherein the blade height above a tissuesurface in contact with the sheath is in a range from 1-10 mm.
 12. Thescalpel cutting device as in claim 1, wherein the blade height above atissue surface in contact with the sheath is in a range from 2.5-7.5 mm.13. A method for trimming a suture comprising, providing a suturecutting device as in claim 1; and drawing a suture through the slotacross the straight cutting edge, thereby trimming the suture length.14. A method as in claim 13, further comprising moving the scalpel bladeto the uncovered position and back to covered position prior to drawingthe suture through the slot.
 15. A method as in claim 14, wherein movingthe scalpel blade to the uncovered position comprises extending theblade beyond the sheath and moving the scalpel blade back to the coveredposition comprises retracting the blade into the sheath.